Many electronic devices such as mouses, remote control devices or keyboards have a left and a right function keys to facilitate browsing of documents, searching of Web pages and zooming of images. In addition, there is a wheel located between the left and the right function keys to output signals during rotation. The operation principle of the wheel is briefed as follow:
Referring to FIG. 1 for a conventional wheel design used in mouses, it has an anchor seat 10 to support a wheel 20. There is an inductive photoelectric switch 12 located below the axle 11. The wheel 20 has a rotation side 22 on a lateral side that has apertures 21 formed thereon in an evenly spaced manner (or as shown in FIG. 2, an axle 11 is connected to a grating switch 15). When the wheel 20 rotates, the apertures 21 break or connect the inductive photoelectric switch 12 to generate different instruction signal outputs. Besides the instruction signal outputs caused by the rotation of the wheel 20, there is a button switch 13 beneath the wheel 20 that allows users to leave the functional window preset by the software to execute other instructions when the button switch 13 is subject to compression from the wheel 20. As the axle 11 and the grating switch 15 usually are fixedly mounted, the downward displacement of the wheel 20 has to take into account of the grating switch 15. This makes design of the wheel 20 more difficult. Moreover, the grating switch 15 or the inductive photoelectric switch 12 is more expensive. Adopted for small mouse, the design of the grating switch 15 or the inductive photoelectric switch 12 is even more complicated.
In addition, rotation of the wheel 20 has to consider the rotation touch sense of users. As shown in FIG. 1, the rotation touch sense is obtained through a rotation end 111 of the axle 11 that has teeth to evenly divide the perimeter of one end of the axle 11. The rotation end 111 is coupled with an elastic reed 14 which bounds over the teeth while the rotation end 111 is rotating to provide the touch sense to users. Such a design increases the cost and makes space design more difficult. Moreover, the rotation end 111 is spaced from the wheel 20 at some distance. The rotation feeling transmitted to the hand of users is not satisfactory.
To meet the trend of electronic products that demands lean and light, U.S. Pat. No. 6,188,389 discloses a mouse structure which has three D shafts input. It mainly includes a main anchor seat, a secondary anchor seat, a rubber wheel, a grating wheel, a suspender and an idle roller. The grating switch is embedded inside between the wheels to shrink the space. It still has the high cost problem of the grating switch. Adopted on small mouses and with the smaller wheels, fabrication of the grating switch is even more difficult.